1. Technical Field
This invention generally relates to milking apparatus that use milking liners to draw milk from the teat. More particularly, the invention is related to the milking liners and the vents used to vent air into the short milk tubes of the milking liners.
2. Background Information
Automatic milking machines have been used to extract milk from different mammals through most of the past century. Most of these machines include a claw that typically has four nipples that are connected to teat cup assemblies that are attached to the teats during the milking process. The teat cup assemblies include a rigid (hard plastic or metal) shell with a resilient, elastomeric milking liner (also known as a milking inflation) disposed within the shell. A short milk tube extends from the liner. A vacuum source is applied to the short milk tube and an alternating vacuum is applied to the shell to cause the liners to collapse and expand and thereby massage the teats and suck milk from the teats. The milk flows from the liners, into the short milk tube, to the nipples of the claw, and from there through a conduit to a collection tank.
As shown in prior art FIGS. 1 and 2, an air vent 2 is used with the short milk tube 4 to prevent the milk 6 in the bottom of the liner barrel 8 or in the short milk tube 4 from being drawn back towards the teat 10 when the barrel 8 expands. A vent plug 2 may be used to provide a venting function to the short milk tube 4. Exemplary vent plugs 2 are shown in U.S. Pat. Nos. 6,055,931, 7,290,498, and 7,293,527. Each of the vent plug structures disclosed in these patents has an outlet 12 configured to direct the vent air into the flowing milk stream 16 of the short milk tube 4. A drawback with these vent plugs is that the vent outlet 12 has a discharge direction that is disposed substantially perpendicular to the flow direction 16 of the milk. The vent air pulled into the short milk tube 4 interferes with smooth laminar milk flow 16 and can reduce milking efficiency.